Unsupported CUDA version 5.0 detected, you need CUDA 6.5
As your /usr/local/ directory shows you have installed multiple versions of CUDA (/usr/bin/nvidia-uninstall would only uninstall the last one). When upgrading I had first to uninstall all CUDA files:

From pre-installation-actions

Use the following command to uninstall a Toolkit runfile installation:

$ sudo /usr/local/cuda-X.Y/bin/uninstall_cuda_X.Y.pl


Use the following command to uninstall a Driver runfile installation:

$ sudo /usr/bin/nvidia-uninstall


Use the following commands to uninstall a RPM/Deb installation:

$ sudo apt-get --purge remove &lt;package_name&gt;          # Ubuntu
$ sudo yum remove &lt;package_name&gt;                      # Fedora/Redhat/CentOS
$ sudo zypper remove &lt;package_name&gt;                   # OpenSUSE/SLES


Check for remaining packages:

$ dpkg -l


and remove them also. After a re-install of the most recent version should work.